All military missiles, whether guided or unguided and whether self-propelled or fired from a gun or other propulsion launcher, for safety reasons are equipped with means for preventing the explosive charge in the missile from becoming armed, i.e. capable of being ignited, until the missile is successfully launched and is well clear of the launching vehicle. Of the many safety and arming mechanisms which have been conceived in the past for this purpose some have been designed to sense the acceleration of the missile as an indication of a successful, or proper, launch. U.S. Pat. Nos. 1,205,921 granted Nov. 21, 1916 to H. Moren for "Safety Device for Shell Fuses", 3,610,154 granted Oct. 5, 1971 to David B. Brown for "Acceleration-Actuated Mechanism", and 3,919,941 granted Nov. 18, 1975 to David S. Breed et al for "Liquid Timing Device" all disclose arming mechanisms which sense acceleration of the missile to initiate an arming procedure. To insure that the missile is clear of the launching vehicle the safety and arming mechanism may also include a timing system to delay arming the missile for a predetermined period of time following successful launch. The aforementioned Brown patent discloses a mechanical movement time delay system for this purpose. The aforementioned Breed et al patent discloses the use of a, so called, sharp edge orifice dashpot traveling through a liquid as a timing mechanism. Prior safety and arming mechanisms as exemplified by the devices disclosed in the Brown and the Breed et al patents, have been rather complex. Complexity usually goes hand in hand with lessened reliability. The more parts a mechanism possesses the more opportunity there is for faulty assembly or component failure to interfere with the intended operation of the mechanism. An extremely high degree of reliability is required for munitions and prior safety and arming mechanisms have often failed to meet that requirement.
A safety and arming mechanism is expendable with the missile so it is desirable to hold the cost of the mechanism to a minimum. And, the more complex the mechanism the more costly the mechanism. This further dictates a demand for a simple, but reliable, safety and arming mechanism.